It is proposed to experimentally investigate the motion of a system composed of a simulated human head and neck when the head is subjected to impact loads representative of those encountered in daily life, including vehicular, sports and industrial environments. The excursion of the head-neck junction is to be determined under these conditions, and the stress distribution in the cross section of the neck and in the head will be ascertained for each of its constituents. An analytical model is to be constructed to represent the physical system, and will be refined until the predictions of the theory for a given impact load are in reasonable accord with experimental data. The purpose of the program is to provide some definitive scientific information on the subject of hyperextension (popularly termed "whiplash"), a traumatic condition experienced annually by millions of victims, as well as to extend previous studies on head response. Although many tests have been executed with anthropometric dummies under acceleration and deceleration conditions, the principal objective of these previous studies has been a delineation of the motion of the head and neck without regard to stress distribution. Furthermore, the data obtained has been essentially restricted to impulsive rather than impact loads and all experimental information has been rationalized on the basis of lumped-mass parameters. The results of the present investigation, which is intended to correct these deficiencies, should be useful not only in the diagnosis of this disability, but should also be directly applicable to the design of protective environments relative to various activities where this dysfunction is frequently encountered.